Technology Field
The disclosure relates to an antenna system and, more particularly, to a Multiple Input Multiple Output (MIMO) antenna system.
Description of the Related Art
Multiple Input Multiple Output (MIMO) antenna system has been widely used. Conventionally, a low-pass filter device and a coupling conductive cable in an antenna system are commonly used to reduce the correlation between a high frequency band and a low frequency band as well as reduce the isolation of each antenna. However, the structure of the antenna system may become quite large due to the low-pass filter device and the coupling conductive cable.
Nowadays, many electrical devices have a tendency towards a smaller size. It is desired to develop a miniaturized MIMO antenna system to meet product specifications. When a conventional planar inverted-F antenna (PIFA) is applied, there might have some problems such as, unideal isolation in a low resonant frequency and a too big envelope correlation coefficient (ECC). Besides, all service providers have different frequency systems, it is desired that a MIMO antenna with great isolation and a small ECC should be developed for a miniaturized device in order to receive and transmit signals in all frequency bands.